Will a 70 amp back feed breaker be enough for the 18kpv?

[TheFlumph]

I had planned on doing the partial home backup with a 70a back feed breaker As detailed in the diagram. Signature solar told me I wouldn’t get my max back feed amount with this setup. upon looking into it further it seems the 18kpv max backfeed is 50a? So it seems to me like the backfeed breaker option should work fine and yield me my max backfeed amount?
is there a reason I should opt for the added expense and complication of doing the whole house backup and feeder tap example from the manual?

 

[Hedges]

Sounds like it will handle same current SolArk could generate.
What it limits is pass-through current from grid, since SolArk has 200A pass through.

If your protected loads downstream of SolArk won't exceed 56A continuous, this is fine.
You can put heavier loads on main panel, not backed up.

You can also put an interlocked backfed "generator" breaker in main panel if you do want to feed those loads from inverter.

I'm not sure if "Hawaiian Tie In" is allowed - remove all breakers from main panel and install a 200A tap in it.

What I'm doing is installing new 200A main breaker only panel (need to upgrade from 100A.)

You also have the option of downsizing your main breaker to 175A or 150A as SolArk's drawing suggests.

 

[TheFlumph]

The critical loads panel I had planned has a 60a breaker. I doubt it would ever hit 56a.
my main concern with this setup is not limiting my backfeed amount to the utility. I don’t want to lose money that way.

 

[Hedges]

80% of 70A is 56A
56A x 240V = 13.44kW continuous. A bit more if voltage is higher.

How much AC can 18kPV make from PV? from PV and battery?
How much PV do you have?

 

[BKY2003]

Maybe they are talking about the 33.6kw that can be back fed with ac coupling

 

[BKY2003]

Biggest drawback of going with the critical load panel is you can only put 13.44kw of cumulative loads, because when there is no solar and the battery is depleted the grid has to carry the loads . I have mine setup with a critical load panel.

 

[TheFlumph]

80% of 70A is 56A
56A x 240V = 13.44kW continuous. A bit more if voltage is higher.

How much AC can 18kPV make from PV? from PV and battery?
How much PV do you have?

About 18kw from solar at max. And the battery is the eg4 power pro.

I’m beginning to think maybe the feeder tap solution might not be a bad option.

 

[TheFlumph]

Maybe they are talking about the 33.6kw that can be back fed with ac coupling

No ac coupling. Just the 12kw backfeed to the grid from PV dc.

 

[TheFlumph]

I think the mistake I’m making is only taking the back feed into account and not the other loads that would be sharing the breaker. I’m new at this and learning a lot from here.
I might be better off just doing the feeder tap from this diagram.

 

[nuke]

I'm running off a critical loads subpanel with a 70a backfeed breaker. During periods of time with no solar or battery support, it means all those critical loads are limited to the 70a feed from the main panel, which could be a problem (especially if you want to charge the battery from the grid). What I did was make the conscious choice to keep my high current draw devices off the critical loads panel. So everything is backed up except the oven, dryer, a/c, pool, and ev charger.

I'm going to let this setup soak for a bit and see if any of it bothers me. My guess is it won't and I'll stop thinking about it.

 

[Hedges]

If you decreased main breaker to 150A, then you could have 120A backfeed. Are we allowed to round up to next standard size 125A when subject to 120% rule?

Inspector called mine "load side tap", Polaris connector after 200A main breaker.

See if you're allowed to just put a 200A tap on the main breaker panel and remove all other breakers.